In recent years, the high-technology electronics manufacturing industries launch more feature-packed and humanized electronic products. These new products that hit the showroom are lighter, thinner, and smaller in design. In the manufacturing of these electronic products, the key component has to be the integrated circuit (IC) chip inside any electronic product.
Rapid development of semiconductor technology has led to rapid progress of a reduction in size of semiconductor packages, the adoption of multi-pin, the adoption of fine pitch, the minimization of electronic components and the like. The purposes and the advantages of wafer level package includes decreasing the production cost, decreasing the effect caused by the parasitic capacitance and parasitic inductance by using the shorter conductive line path, acquiring better SNR (i.e. signal to noise ratio). Furthermore, the size of a wafer-level package product is close to the size of a chip, and therefore, the size of the chip determines the package volume.
Conventionally, the function of chip package includes power distribution, signal distribution, heat dissipation, protection and support. As a semiconductor becomes more complicated, the traditional package technique, for example lead frame package, flex package, and rigid package techniques, cannot meet the demand of producing a smaller chip with high density elements on the chip.
The chip-scale package (CSP) has been conventionally formed by a method in which a semiconductor wafer is cut into semiconductor chips, then the semiconductor chips are mounted on a base substrate serving as a package base at predetermined positions and bonded thereto, and they are collectively sealed with a resin, thereafter the sealing resin and the base substrate are cut into pieces together at the parts between the semiconductor chips. In another conventional method, a semiconductor wafer (not yet being cut into semiconductor chips) is mounted on a base substrate and bonded thereto, then the semiconductor wafer and the base substrate are cut simultaneously, and the cut and divided semiconductor chips and package bases are sealed with a resin.
Further, the operability, performance, and life of an IC chip are greatly affected by its circuit design, wafer manufacturing, and chip packaging. For the present invention, the focus will be on chip packaging technique. Since the features and speed of IC chips are increasing rapidly, the need for increasing the conductivity of the circuitry is necessary so that the signal delay and attenuation of the dies to the external circuitry are reduced. A chip package that allows good thermal dissipation and protection of the IC chips with a small overall dimension of the package is also necessary for higher performance chips. These are the goals to be achieved in chip packaging.
There are a vast variety of existing chip package techniques such as ball grid array (BGA), wire bonding, flip chip for mounting a die on a substrate via the bonding points on both the die and the substrate. The inner traces help to fan out the bonding points on the bottom of the substrate. The solder balls are separately planted on the bonding points for acting as an interface for the die to electrically connect to the external circuitry. Similarly, pin grid array (PGA) is very much like BGA, which replaces the balls with pins on the substrate and PGA also acts an interface for the die to electrically connect to the external circuitry.
Both BGA and PGA packages require wiring or flip chip for mounting the die on the substrate. The inner traces in the substrate fan out the bonding points on the substrate, and electrical connection to the external circuitry is carried out by the solder balls or pins on the bonding points. As a result, this method fails to reduce the distance of the signal transmission path but in fact increase the signal path distance. This will increase signal delay and attenuation and decrease the performance of the chip.
However, in the manufacturing method, wafer level chip scale package (WLCSP) has an advantage of being able to print the redistribution circuit directly on the die by using the peripheral area of the die as the bonding points. It is achieved by redistributing an area array on the surface of the die, which can fully utilize the entire area of the die. The bonding points are located on the redistribution circuit by forming flip chip bumps so the bottom side of the die connects directly to the printed circuit board (PCB) with micro-spaced bonding points.
Although WLCSP can greatly reduce the signal path distance, it is still very difficult to accommodate all the bonding points on the die surface as the integration of die and internal components gets higher. The pin count on the die increases as integration gets higher so the redistribution of pins in an area array is difficult to achieve. Even if the redistribution of pins is successful, the distance between pins will suffer yield and reliability issues owing to the huge size of the package. The further disadvantages of the former method are higher costs and time-consuming for manufacture.
Therefore, the present invention provides a new structure and method for a package that minimizes the thickness of package structure for a wafer level package to overcome the aforementioned problem.